A crystalline silicon-based solar cell including a conductive silicon-based thin-film on a single-crystalline silicon substrate is called a heterojunction solar cell. Particularly, a heterojunction solar cell including an intrinsic amorphous silicon thin-film between a conductive silicon-based thin-film and a crystalline silicon substrate is known as one of forms of crystalline silicon-based solar cells having the highest conversion efficiency.
A heterojunction solar cell includes silicon-based thin-film of opposite-conductivity-type on the light-receiving side of a crystalline silicon substrate of first conductivity-type, and silicon-based thin-film of first conductivity-type on the back side of the crystalline silicon substrate of first conductivity-type. Generally, an n-type crystalline silicon substrate is used, and a p-type silicon-based thin-film is formed on the light-receiving side thereof, while an n-type silicon-based thin-film is formed on the back side thereof. Carriers generated at these semiconductor junction portions are extracted outside of a solar cell via an electrode. As the electrode, a combination of a transparent electrode layer and a metal collecting electrode is generally used.
As described in Patent Document 2, deposition of a silicon-based thin-film is generally performed by mounting a plurality of silicon substrates on a plate-shape tray. Particularly when a mask or the like is not used in deposition, the transparent electrode layer is also deposited on the lateral surface of a silicon substrate or on a side opposite to a major deposition surface of the silicon substrate by wraparound, so that a short circuit occurs between the front and the back. Patent Document 1 suggests that when a front-side transparent electrode layer is formed with a mask disposed on the peripheral end of a silicon substrate, a short circuit between the front and the back can be prevented because the transparent electrode layer is not formed on the peripheral end of the silicon substrate.
Since the metal collecting electrode shields light, a line-shape patterned metal collecting electrode is used on the light-receiving side for enlarging the light-receiving area of the solar cell. For example, Patent Document 3 discloses a heterojunction solar cell in which a metal electrode is formed by electroplating. In electroplating, a metal electrode having a large thickness can be easily formed, and therefore improvement of characteristics and productivity by reduction of the resistance of the metal electrode can be expected.